package com.kun.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

//操作数据库的公共类
public class BaseDao {

    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    //静态代码块 类加载的时候就初始化了
    static {
        InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");
        Properties properties = new Properties();

        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }

        driver = properties.getProperty("driver");
        url = properties.getProperty("url");
        username = properties.getProperty("username");
        password = properties.getProperty("password");
    }

    //获取数据库的连接
    public static Connection getConnection(){
        Connection connection = null;

        try {
            Class.forName(driver);
            connection = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return connection;
    }

    //编写查询公共类
    public static ResultSet executeQuery(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet,String sql,Object[] params) throws SQLException {
        //预编译sql
        preparedStatement = connection.prepareStatement(sql);;

        if(params != null){
            for (int i = 0; i < params.length; i++) {
                //setObject，占位符从1开始
                preparedStatement.setObject(i+1,params[i]);
            }
        }

        resultSet = preparedStatement.executeQuery();

        return resultSet;
    }

    //编写增删改公共方法
    public static int executeUpdate(Connection connection,PreparedStatement preparedStatement,String sql,Object[] params) throws SQLException {
        //预编译sql
        preparedStatement = connection.prepareStatement(sql);;

        for (int i = 0; i < params.length; i++) {
            //setObject，占位符从1开始
            preparedStatement.setObject(i+1,params[i]);
        }

        return preparedStatement.executeUpdate();
    }


    /**
     * 释放资源
     * @param connection        数据库连接
     * @param preparedStatement 预编语句
     * @param resultSet         返回的查询集合
     * @return  如果存在一个关闭异常则返回false，正常关闭则返回true
     */
    public static boolean closeResource(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet){
        return closeResource(resultSet)
                &&closeResource(preparedStatement)
                &&closeResource(connection);
    }

    public static boolean closeResource(PreparedStatement preparedStatement,ResultSet resultSet){
        return closeResource(resultSet)
                &&closeResource(preparedStatement);
    }

    public static boolean closeResource(ResultSet resultSet){
        if(resultSet != null){
            try {
                resultSet.close();
                //GC回收
                resultSet = null;
            } catch (SQLException e) {
                e.printStackTrace();
                return false;
            }
        }
        return true;
    }

    public static boolean closeResource(Connection connection){
        if(connection != null){
            try {
                connection.close();
                //GC回收
                connection = null;
            } catch (SQLException e) {
                e.printStackTrace();
                return false;
            }
        }
        return true;
    }

    public static boolean closeResource(PreparedStatement preparedStatement){
        if(preparedStatement != null){
            try {
                preparedStatement.close();
                //GC回收
                preparedStatement = null;
            } catch (SQLException e) {
                e.printStackTrace();
                return false;
            }
        }
        return true;
    }

}
